Debt (Details 2) (USD $)	9 Months Ended	12 Months Ended
	Nov. 30, 2014	Feb. 28, 2014
Long-term debt
Total long-term debt	115,707,000	192,607,000
Less current maturities of long-term debt	(21,900,000)	(96,900,000)
Long-term debt, excluding current maturities	93,807,000	95,707,000
Unsecured MBFC Loan
Long-term debt
Face amount	37,610,000
Interest rate (as a percent)	2.28%
Total long-term debt	35,707,000	37,607,000
Unsecured MBFC Loan | Base Rate
Long-term debt
Variable Rate Basis	Base Rate
Unsecured MBFC Loan | Base Rate | Maximum
Long-term debt
Basis spread on variable rate (as percent)	1.125%
Unsecured MBFC Loan | LIBOR
Long-term debt
Variable Rate Basis	LIBOR
Unsecured MBFC Loan | LIBOR | Maximum
Long-term debt
Basis spread on variable rate (as percent)	2.125%
Unsecured floating interest rate Senior Notes due June 2014
Long-term debt
Face amount		75,000,000
Total long-term debt		75,000,000
Unsecured floating interest rate Senior Notes due June 2014 | LIBOR
Long-term debt
Basis spread on variable rate (as percent)		0.90%
Variable Rate Basis		three month LIBOR
Unsecured floating interest rate Senior Notes due June 2014 | Interest rate swaps
Long-term debt
Interest rate (as a percent)		6.01%
3.90% unsecured Senior Notes
Long-term debt
Face amount	100,000,000
Interest rate (as a percent)	3.90%
Interest rate (as a percent)	3.90%
Frequency of principal payment	Annual
Principal payments	20,000,000
Total long-term debt	80,000,000	80,000,000